Research conducted over the last decade has helped elucidate the molecular events attending cell-cell interactions in the body, especially those events involved in the movement and activation of cells in the immune system. See generally, Springer, T. Nature, 1990, 346, 425-434. Cell surface proteins, and especially the Cellular Adhesion Molecules (“CAMs”) and “leukointegrins”, including LFA-1, MAC-1 and gp150.95 (referred to as CD18/CD11a, CD18/CD11b, and CD18/CD11c, respectively) have correspondingly been the subject of pharmaceutical research and development having as its goal the intervention in the processes of leukocyte extravasation to sites of injury and leukocyte movement to distinct targets. For example, it is presently believed that prior to the leukocyte extravasation, which is a mandatory component of the inflammatory response, activation of integrins constitutively expressed on leukocytes occurs and is followed by a tight ligand/receptor interaction between integrins (e.g., LFA-1) and one or several distinct intercellular adhesion molecules (ICAMs) designated ICAM-1, ICAM-2, ICAM-3 or ICAM-4 which are expressed on blood vessel endothelial cell surfaces and on other leukocytes. The interaction of the CAMs with the leukointegrins is a vital step in the normal functioning of the immune system. It is believed that immune processes such as antigen presentation, T-cell mediated cytotoxicity and leukocyte extravasation all require cellular adhesion mediated by ICAMs interacting with the leukointegrins. See generally Kishimoto, T. K.; Rothlein; R. R. Adv. Pharmacol. 1994, 25, 117-138 and Diamond, M.; Springer, T. Current Biology, 1994, 4, 506-532.
Clearly, because of the role that the interaction of the CAMs and the leukointegrins plays in the immune response, it would be desirable to modulate these specific interactions to achieve a desired therapeutic result (e.g., inhibition of the interaction in the event of an overactive immune response). Significantly, it has been demonstrated that the antagonism of the interaction between the CAMs and the leukointegrins can be realized by agents directed against either component. Specifically, blocking of the CAMs, such as for example ICAM-1, or the leukointegrins, such as for example LFA-1, by antibodies directed against either or both of these molecules effectively inhibits inflammatory responses. In vitro models of inflammation and immune response inhibited by antibodies to CAMs or leukointegrins include antigen or mitogen-induced lymphocyte proliferation, homotypic aggregation of lymphocytes, T-cell mediated cytolysis and antigen-specific induced tolerance. The relevance of the in vitro studies are supported by in vivo studies with antibodies directed against ICAM-1 or LFA-1. For example, antibodies directed against LFA-1 can prevent thyroid graft rejection and prolong heart allograft survival in mice (Gorski, A.; Immunology Today, 1994, 15, 251-255). Of greater significance, antibodies directed against ICAM-1 have shown efficacy in vivo as anti-inflammatory agents in human diseases such as renal allograft rejection and rheumatoid arthritis (Rothlein, R. R.; Scharschmidt, L., in: Adhesion Molecules; Wegner, C. D., Ed.; 1994, 1-38, Cosimi, C. B.; et al., J. Immunol. 1990, 144, 4604-4612 and Kavanaugh, A.; et al., Arthritis Rheum. 1994, 37, 992-1004) and antibodies directed against LFA-1 have demonstrated immunosuppressive effects in bone marrow transplantation and in the prevention of early rejection of renal allografts (Fischer, A.; et al., Lancet, 1989, 2, 1058-1060 and Le Mauff, B.; et al., Transplantation, 1991, 52, 291-295).
As described above, the use of anti-LFA-1 or anti-ICAM-1 antibodies to antagonize this interaction has been investigated. Additionally, the use of LFA-1 or ICAM-1 peptides, fragments or peptide antagonists (see, for example, U.S. Pat. Nos. 5,149,780, 5,288,854, 5,340,800, 5,424,399, 5,470,953, Published PCT applications WO 90/03400, WO90/13316, WO90/10652, WO91/19511, WO92/03473, WO94/11400, WO95/28170, JP4193895, EP314863, EP362526, EP362531), and small molecule antagonists have been investigated. For example, several small molecules have been described in the literature which affect the interaction of CAMs and leukointegrins. A natural product isolated from the root of Trichilia rubra was found to be inhibitory in an in vitro cell binding assay (Musza, L. L.; et al., Tetrahedron, 1994, 50, 11369-11378). One series of molecules (Boschelli, D. H.; et al., J. Med. Chem. 1994, 37, 717 and Boschelli, D. H.; et al., J. Med. Chem. 1995, 38, 4597-4614) was found to be orally active in a reverse passive Arthus reaction, an induced model of inflammation that is characterized by neutrophil accumulation (Chang, Y. H.; et al., Eur. J. Pharmacol. 1992, 69, 155-164). Another series of molecules was also found to be orally active in a delayed type hypersensitivity reaction in rats (Sanfilippo, P. J.; et al., J. Med. Chem. 1995, 38, 1057-1059). All of these molecules appear to act nonspecifically, either by inhibiting the transcription of ICAM-1 along with other proteins or act intracellularly to inhibit the activation of the leukointegrins by an unknown mechanism, and none appear to directly antagonize the interaction of the CAMs with the leukointegrins.
Clearly, although several classes of compounds have been investigated for therapeutic use, there remains a need for the development of novel therapeutics that are capable of modulating interactions between CAMs and leukointegrins. In particular, it would be desirable to develop therapeutics capable of selectively targeting (preferably inhibiting) the interaction between LFA-1 and ICAM-1 that would be useful as a therapeutic agent for immune and/or inflammatory disorders.